Acute studies in man and experimental animals have demonstrated phasic contractions of the sphincter of Oddi (SO) which correlate with fluctuations in delivery of bile to the duodenum. The long-term motor pattern of the SO in either the fasted or fed state, however, is unknown. The specific aims of this proposal, therefore, are to l) develop a chronic preparation in the opossum for the study of biliary myoelectric and motor activity; 2) define the relationship between the interdigestive myoelectric patterns of the SO, small intestine, and stomach; 3) determine the effect of exogenous motilin on the interdigestive myoelectric pattern of the SO; 4) determine the postprandial pattern of SO myoelectric activity and the coordination of gastric emptying, gallbladder (GB) contraction and SO motor activity; and 5) compare SO motility before and after cholecystectomy. To realize these aims, opossums will be prepared with electrodes secured to the SO, stomach, duodenum and jejunum. Cannulae will be inserted into the lumens of the GB and common bile duct (CD) and dual catheters will be inserted into the duodenum. Myoelectric activity of the SO, stomach, duodenum and small intestine will be recorded continuously in fasted animals and the relationship between gastrointestinal migrating myoelectric complexes and the myoelectric activity of the SO determined. Fasting studies will be repeated during infusion of exogenous motilin. In fed studies, SO and intestinal myoelectric activity, GB and CD pressure, duodenal bile acid output, and the rate of gastric emptying will be simultaneously recorded. A double isotope duodenal perfusion technique will be utilized to quantitate gastric emptying and bile acid output. Postprandial studies will be repeated after cholecystectomy. This chronic opossum preparation will better define the physiological relationship between fasting and fed motor patterns of the biliary tract, stomach and small intestine. It will provide the framework for the study of pathophysiologic disorders of the biliary system and pancreas.